Cu,Zn superoxide dismutase (SOD) mutations can cause Familial Amyotrophic Lateral Sclerosis (FALS), an inherited variety of ALS (or Lou Gehrig's disease), the most common human motor neuron disease. We, and others have discovered that FALS SOD mutants have defects in fold and assembly, and form fibrous aggregates. Together our SOD results including comparative analyses of human Cu,ZnSOD, MnSOD and microbial SODs, plus other published data including binding of FALS mutant SOD to stress response proteins Rac1 and Derlin-1, suggest that local structural defects from FALS mutations promote toxicity via aggregation and aberrant protein binding. Characterization of the thermostable eukaryotic SOD from Alvinella pompejana reveals that extra interactions that reduce local unraveling of loops and termini improve SOD biochemical and biological stability. This proposal has three goals: 1) to develop a unified understanding for the SOD mutations that can cause FALS, 2) to test protein partner roles in aberrant SOD structural biochemistry, and 3) to identify and characterize ligands that stabilize FALS mutant SODs to reduce their toxicity. The Tainer and Shin labs will produce FALS SOD mutant proteins and analyze them by small angle X-ray scattering (SAXS) and fluorescent screening to test possible unified molecular mechanisms for pathophysiology. The Getzoff and Shin labs will solve and analyze crystal structures informed by NMR results, examine protein interactions and conformations with deuterium exchange mass spectrometry, and employ computer-based ligand binding analyses. Together, the coordinated Tainer-Getzoff-Shin efforts aim to resolve paradoxes concerning the molecular mechanism by which >100 SOD mutations lead to the same FALS pathology, and to discover and optimize ligands as chemical tools that reduce FALS SOD mutant aggregation and toxicity. PUBLIC HEALTH RELEVANCE: Many different mutations in the human protein Cu,Zn superoxide dismutase (SOD) can cause the late-onset neurodegenerative disease amyotrophic lateral sclerosis (ALS) or Lou Gehrig's disease. Most ALS victims die within a few years, and there is no effective treatment. Our research has two overall goals: 1) to understand how SOD mutations result in aberrant protein interactions and assemblies that underlie ALS pathophysiology, and 2) to discover chemical ligands that stabilize the normal SOD fold and assembly as candidate compounds that may slow or prevent disease progression.